West Nile-carrying mosquitoes back in season
The summertime doesn’t just draw more people outdoors. The hot season also drives the mosquito population, especially after heavy rainfall events.
So around this time of year, public health departments throughout Illinois as well as some local communities launch mosquito control efforts to ward off both the nuisance, as well as the threat of West Nile virus.
The virus is transmitted from the bite of a mosquito that became infected after feeding on an infected bird.
“We are starting to see West Nile virus in mosquitoes and birds, and when temperatures rise and conditions dry up, we typically see increased reports of West Nile virus,” said Damon Arnold, director of the Illinois Department of Public Health.
Since this year’s surveillance program – which involves laboratory testing of samples – began in May, five Illinois counties turned up positive West Nile virus samples.
Positive mosquito samples were collected from Cook, Kendall, Tazewell and St. Clair counties. And birds that tested positive for West Nile virus were collected from LaSalle County, according to the Illinois Department of Public Health.
In McHenry County, three birds were sent in for testing and all turned negative, said Maryellen Howell, county health department coordinator. Testing of vector mosquitoes, located at seven traps throughout McHenry County, is ongoing.
So far this year in Illinois, there have not been any human cases of the virus reported. Last year, 61 human cases of West Nile disease were reported in Illinois, according to the state health department.
Symptoms of the illness can appear from three to 15 days after the infected bite. Centers for Disease Control and Prevention officials say most people, about 80 percent, who get infected do not see any symptoms. Mild symptoms improve on their own.
Mild symptoms include high fever, dizziness, body aches and numbness. Infection could lead to serious illnesses, however, such as meningitis and even death. People older than 50 have the highest risk of severe disease.
Although serious illness and death are possible, health officials say only about two out of 10 people bitten by an infected mosquito will experience any symptoms.
Instead of spraying, the McHenry County Department of Health uses larvicide pellets to keep the mosquito population down. These pellets are dropped into stagnant water and catch basins – mosquito breeding grounds.
“It is difficult to productively spray mosquitoes because mosquitoes travel a long way,” Howell said. “A mosquito can be in McHenry County today and travel to another surrounding county tomorrow. Vice versa, another county’s mosquitoes can arrive in McHenry County.”
Municipalities also have their own mosquito control and abatement programs. In the village of Fox River Grove, the “strategic larvicide application program takes care of the [West Nile virus] threat,” Village Administrator Art Osten Jr. said.
Fox River Grove has 585 catch basins where larvicide pellets are placed. And of those sites, 150 hold water on a regular basis.
Because three out of a mosquito’s four life cycles is spent either in or on the surface of water, communities near bodies of water tend to prioritize mosquito abatement and control efforts.
“We’re right along the Fox River and streams and ponds run through the village, and there are wetlands,” Osten said.
For about eight years, the village sprayed and used pellets to ward off mosquitoes. Then in recent years, the village discontinued the sprays “because it’s not very effective.”
“[Spraying] only kills the mosquitoes it lands on,” Osten said.
Village officials say that based on the village’s larvicide program, the virus is a “low-level threat.”
Like Fox River Grove, the city of Crystal Lake also takes mosquito abatement seriously. There are six trap locations in the city, said A.J. Reineking, assistant to the city’s public works director.
“We have lots of bodies of water and wetlands which are conducive to mosquito breeding,” he said.
The city contracts with Clarke mosquito control professionals to administer the integrated abatement program, which runs from late spring through early fall.
Clarke, based in Roselle, has been providing mosquito control services to several McHenry County municipalities since 1946. Besides Crystal Lake, other local government clients include Huntley, Lake in the Hills, Woodstock, Johnsburg, McHenry Township, the city of McHenry and Algonquin Township.
George Balis, a Clarke entomologist, said that in McHenry County, there almost are 40 species of mosquitoes. Of those, it’s primarily the Culex species, which breeds in standing water, that carries West Nile.
But it takes only “little steps” to reduce the risk of a virus infection and cut down the mosquito population overall, Balis said.
Look around for any stagnant water and simply “tip and toss” the water out, he said. Sources of standing water include receptacles found in backyards, such as birdbaths, wading pools and wheelbarrows.
Health departments suggest people avoid being outdoors from dusk to dawn, when mosquitoes are most active.
Replace or repair windows and doors that have openings, wear long sleeves and apply insect repellents. But consult a physician before using repellents on infants.
To learn more
• Centers for Disease Control and Prevention’s West Nile Virus page: www.cdc.gov/ncidod/dvbid/westnile
• Illinois Department of Public Health: www.idph.state.il.us/envhealth/wnv.htm
West Nile prevention tips
Tips to prevent or reduce the risk of infection:
• Avoid being outdoors from dusk to dawn, when mosquitoes are most active.
• Replace or repair windows and doors that have any openings.
• Wear long sleeves and apply insect-repellent products. But consult a physician before applying repellents on infants.
• To thwart mosquito breeding, remove areas of standing water where possible.
Sources: Centers for Disease Control and Prevention,
Illinois Department of Public Health